E-isomer of 1-(4-methylphenyl)-1-(2-pyridyl)-3-pyrrolidinoprop-1-ene (Formula I) exhibits anti-histamine activity.

U.S. Pat. No. 2,712,023 disclose a process for preparing E-isomer of 1-(4-methylphenyl)-1-(2-pyridyl)-3-pyrrolidinoprop-1-ene (Formula I) from 1-(4-methylphenyl)-1-(2-pyridyl)-3-pyrrolidinopropan-1-ol (Formula III). 4-methyl-ω-pyrrolidinopropiophenone required for the preparation of the carbinol is prepared by Mannich reaction from 4-methyl acetophenone and pyrrolidine. 1-(4-Methylphenyl)-1-(2-pyridyl)-3-pyrrolidinopropan-1-ol is heated at 165° C. for 10 minutes with aqueous sulphuric acid (85%, 20 cc). The solution is then poured on to crushed ice, basified with excess ammonia solution and the liberated oil is extracted with light petroleum (B.P. 60-80°). The extract is dried over anhydrous sodium sulphate and the solvent is evaporated to leave amber syrup consisting of the E and Z isomers of 1-(4-methylphenyl)-1-(2-pyridyl)-3-pyrrolidinoprop-1-ene. The mixture of isomers is passed onto a column of sulphonated cross-linked polystyrene to isolate the isomers. The isomers are converted to their oxalates and recrystallisation of trans isomer oxalate from methanol gave pure oxalate of trans isomer of 1-(4-methylphenyl)-1-(2-pyridyl)-3-pyrrolidinoprop-1-ene.
U.S. Pat. No. 2,712,023 disclose that separation of the isomers can be accomplished by a number of methods, e.g., fractional crystallization, chromatographic method or separation by Base Exchange Chromatography.
Normally, when separation methods such as column chromatography are used in order to separate compounds from a mixture, it is observed that these methods are associated with the use of large volumes of solvents resulting in a process of longer duration and the subsequent purifications steps for the removal of excess solvents.
Indian Patent Application No. 992/CHE/2006 discloses a process for preparation of E-isomer of 1-(4-methylphenyl)-1-(2-pyridyl)-3-pyrrolidinoprop-1-ene by reacting 2-(1-pyrrolidino)ethyl triphenyl phosphonium bromide with 2-(p-toluoyl)pyridine in presence of an aprotic solvent and a base followed by isomerization in presence of an acid catalyst.